The invention relates generally to electronic circuits, and more particularly to a redundant oscillator and method for generating a phase-regulated signal. For example, such an oscillator may generate a regulated signal having the same phase as a majority of multiple reference signals. Therefore, a phase shift in a minority of the reference signals does not affect the phase of the regulated signal.
Integrated circuits (ICs) that operate in harsh environments such as outer space may temporarily or permanently fail in response to an environmental disturbance such as radiation. For example, a single-event transient (SET) is defined as a charged particle striking a circuit node inside an IC. Typically, the charged particle imparts a temporary charge to the circuit node, and this charge may temporarily affect the phase, frequency, amplitude, or other parameter of a signal that propagates through the node. Depending on the function, path, and affected parameter of the signal, one or more circuits within the IC may temporarily or permanently fail, thus causing the IC itself to fail. For example, a temporary shift in the phase of a data clock may force a data circuit out of synchronization with other circuits, and thus may cause the IC to generate erroneous data.
In one aspect of the invention, a circuit includes a signal generator and a discriminator. The signal generator generates a plurality of reference signals where at least a majority of the reference signals have the same phase. The discriminator generates a regulated signal that has the same phase as the majority of the reference signals. For example, a redundant oscillator circuit can have a signal generator that generates three reference signals all having the same phase and frequency. Therefore, if a disturbance such as an SET temporarily shifts the phase or phases of a minority of the reference signals, the phase of the regulated signal does not shift because the discriminator references the regulated signal to the undisturbed majority of the reference signals.